Aerotolerant anaerobe

Anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth:
1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.
2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration.
4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen, they gather in the upper part of the test tube but not the very top.
5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen, they can be found evenly spread throughout the test tube.

Aerotolerant anaerobes use fermentation to produce ATP. They do not utilize oxygen, but they can protect themselves from reactive oxygen molecules; in contrast, obligate anaerobes can be harmed by reactive oxygen molecules.

There are three categories of anaerobes. Obligate anaerobes are damaged by the presence of oxygen. Aerotolerant organisms cannot use oxygen for growth but are tolerate its presence. And facultative anaerobes can grow without oxygen but use oxygen if it is present.

1.
Bacteria
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Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process. In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, syphilis, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are also used in farming, making antibiotic resistance a growing problem. Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, however, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea, here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea

2.
Thioglycolate broth
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Thioglycolate broth is a multipurpose, enriched, differential medium used primarily to determine the oxygen requirements of microorganisms. Sodium thioglycolate in the medium consumes oxygen and permits the growth of obligate anaerobes and this, combined with the diffusion of oxygen from the top of the broth, produces a range of oxygen concentrations in the medium along its depth. The oxygen concentration at a level is indicated by a redox-sensitive dye such as resazurine that turns pink in the presence of oxygen. This allows the differentiation of obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, for example, obligately anaerobic Clostridium species will be seen growing only in the bottom of the test tube. Thioglycolate broth is used to recruit macrophages to the peritoneal cavity of mice when injected intraperitoneally. It recruits numerous macrophages, but does not activate them

3.
Obligate aerobe
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An obligate aerobe is an organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to metabolise substances, like sugars or fats, in this type of respiration, oxygen serves as the terminal electron acceptor for the electron transport chain. Aerobic respiration has the advantage of yielding more energy than fermentation or anaerobic respiration, examples of obligately aerobic bacteria include Mycobacterium tuberculosis and Nocardia asteroides. With the exception of the yeasts, most fungi are obligate aerobes, also, almost all algae are obligate aerobes. Aerobic respiration Anaerobic respiration Fermentation Obligate anaerobe Facultative anaerobe Microaerophile

4.
Obligate anaerobe
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Obligate anaerobes are microorganisms killed by normal atmospheric concentrations of oxygen. Oxygen tolerance varies between species, some capable of surviving in up to 8% oxygen, others losing viability unless the oxygen concentration is less than 0. 5%, an important distinction needs to be made here between the obligate anaerobes and the microaerophiles. Microaerophiles, like the obligate anaerobes, are damaged by normal atmospheric concentrations of oxygen, however, microaerophiles metabolise energy aerobically, and obligate anaerobes metabolise energy anaerobically. Microaerophiles therefore require oxygen for growth, aerobic organisms produce superoxide dismutase and catalase to detoxify these products, but obligate anaerobes produce these enzymes in very small quantities, or not at all. Dissolved oxygen increases the potential of a solution, and high redox potential inhibits the growth of some obligate anaerobes. Organisms may not be able to grow with these essential enzymes deactivated, growth may be inhibited due to a lack of reducing equivalents for biosynthesis, because electrons are exhausted in reducing oxygen. Obligate anaerobes metabolise energy by anaerobic respiration or fermentation, in aerobic respiration, the pyruvate generated from glycolysis is converted to acetyl-CoA. This is then broken down via the TCA cycle and electron transport chain, Anaerobic respiration differs from aerobic respiration in that it uses an electron acceptor other than oxygen in the electron transport chain. Examples of alternative electron acceptors include sulfate, nitrate, iron, manganese, mercury, Fermentation differs from anaerobic respiration in that the pyruvate generated from glycolysis is broken down without the involvement of an electron transport chain. Numerous fermentation pathways exist e. g. lactic acid fermentation, mixed acid fermentation, the energy yield of anaerobic respiration and fermentation is less than in aerobic respiration. This is why facultative anaerobes, which can metabolise energy both aerobically and anaerobically, preferentially metabolise energy aerobically and this is observable when facultative anaerobes are cultured in thioglycollate broth. Examples of obligately anaerobic bacterial genera include Actinomyces, Bacteroides, Clostridium, Fusobacterium, Peptostreptococcus, Porphyromonas, Prevotella, Propionibacterium, Clostridium species are endospore-forming bacteria, and can survive in atmospheric concentrations of oxygen in this dormant form. The remaining bacteria listed do not form endospores, examples of obligately anaerobic fungal genera include the rumen fungi Neocallimastix, Piromonas, and Sphaeromonas. Aerobic respiration Anaerobic respiration Fermentation Obligate aerobe Facultative anaerobe Microaerophile

5.
Microaerophile
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A microaerophile is a microorganism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere. Many microaerophiles are also capnophiles, requiring an elevated concentration of carbon dioxide, microaerophiles can be cultivated in candle jars. Candle jars are containers into which a lit candle is introduced before sealing the containers airtight lid, the candles flame burns until extinguished by oxygen deprivation, creating a carbon dioxide-rich, oxygen-poor atmosphere. Other methods of creating a microaerobic environment include using a gas-generating pack, helicobacter pylori, a species of proteobacteria that has been linked to peptic ulcers and some types of gastritis

6.
Fermentation
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Fermentation is a metabolic process that converts sugar to acids, gases, or alcohol. It occurs in yeast and bacteria, and also in oxygen-starved muscle cells, Fermentation is also used more broadly to refer to the bulk growth of microorganisms on a growth medium, often with the goal of producing a specific chemical product. French microbiologist Louis Pasteur is often remembered for his insights into fermentation, the science of fermentation is known as zymology. Fermentation takes place when the transport chain is unusable. In this case it becomes the primary means of ATP production. Fermentation turns NADH and pyruvate produced in glycolysis into NAD+. In the presence of O2, NADH and pyruvate are used to generate ATP in respiration and this is called oxidative phosphorylation, and it generates much more ATP than glycolysis alone. For that reason, cells generally benefit from avoiding fermentation when oxygen is available, the exception being obligate anaerobes which cannot tolerate oxygen. The first step, glycolysis, is common to all fermentation pathways, two ADP molecules and two Pi are converted to two ATP and two water molecules via substrate-level phosphorylation. Two molecules of NAD+ are also reduced to NADH, in oxidative phosphorylation the energy for ATP formation is derived from an electrochemical proton gradient generated across the inner mitochondrial membrane via the electron transport chain. Humans have used fermentation to produce drinks and beverages since the Neolithic age, Fermentation can even occur within the stomachs of animals, such as humans. To many people, fermentation simply means the production of alcohol, grains and fruits are fermented to produce beer, if a food soured, one might say it was off or fermented. Here are some definitions of fermentation and they range from informal, general usage to more scientific definitions. Preservation methods for food via microorganisms, any process that produces alcoholic beverages or acidic dairy products. Any large-scale microbial process occurring with or without air, any energy-releasing metabolic process that takes place only under anaerobic conditions. Fermentation does not necessarily have to be carried out in an anaerobic environment, for example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to aerobic respiration, as long as sugars are readily available for consumption. The antibiotic activity of hops also inhibits aerobic metabolism in yeast, Fermentation reacts NADH with an endogenous, organic electron acceptor. Usually this is formed from the sugar during the glycolysis step. Sugars are the most common substrate of fermentation, and typical examples of products are ethanol, lactic acid, carbon dioxide

7.
Adenosine triphosphate
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Adenosine triphosphate is a nucleotide, also called a nucleoside triphosphate, is a small molecule used in cells as a coenzyme. It is often referred to as the unit of currency of intracellular energy transfer. ATP transports chemical energy within cells for metabolism, most cellular functions need energy in order to be carried out, synthesis of proteins, synthesis of membranes, movement of the cell, cellular division, transport of various solutes etc. The ATP is the molecule that carries energy to the place where the energy is needed, when ATP breaks into ADP and Pi, the breakdown of the last covalent link of phosphate liberates energy that is used in reactions where it is needed. Substrate-level phosphorylation, oxidative phosphorylation in cellular respiration, and photophosphorylation in photosynthesis are three mechanisms of ATP biosynthesis. Metabolic processes that use ATP as an energy source convert it back into its precursors, ATP is therefore continuously recycled in organisms, the human body, which on average contains only 250 grams of ATP, turns over its own body weight equivalent in ATP each day. ATP is used as a substrate in signal transduction pathways by kinases that phosphorylate proteins and it is also used by adenylate cyclase, which uses ATP to produce the second messenger molecule cyclic AMP. The ratio between ATP and AMP is used as a way for a cell to sense how much energy is available and control the metabolic pathways that produce and consume ATP. Apart from its roles in signaling and energy metabolism, ATP is also incorporated into nucleic acids by polymerases in the process of transcription, ATP is the neurotransmitter believed to signal the sense of taste. The structure of this consists of a purine base attached by the 9′ nitrogen atom to the 1′ carbon atom of a pentose sugar. Three phosphate groups are attached at the 5′ carbon atom of the pentose sugar and it is the addition and removal of these phosphate groups that inter-convert ATP, ADP and AMP. When ATP is used in DNA synthesis, the sugar is first converted to deoxyribose by ribonucleotide reductase. ATP was discovered in 1929 by Karl Lohmann, and independently by Cyrus Fiske and Yellapragada Subbarow of Harvard Medical School and it was proposed to be the intermediary molecule between energy-yielding and energy-requiring reactions in cells by Fritz Albert Lipmann in 1941. It was first artificially synthesized by Alexander Todd in 1948, ATP consists of adenosine – composed of an adenine ring and a ribose sugar – and three phosphate groups. The phosphoryl groups, starting with the group closest to the ribose, are referred to as the alpha, beta, consequently, it is closely related to the adenosine nucleotide, a monomer of RNA. ATP is highly soluble in water and is stable in solutions between pH6.8 and 7.4, but is rapidly hydrolysed at extreme pH. Consequently, ATP is best stored as an anhydrous salt, ATP is an unstable molecule in unbuffered water, in which it hydrolyses to ADP and phosphate. This is because the strength of the bonds between the groups in ATP is less than the strength of the hydrogen bonds, between its products, and water

8.
Oxygen
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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products

9.
Anaerobic organism
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An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present, an anaerobic organism may be unicellular or multicellular. Van Leeuwenhoek sealed one of the tubes by using a flame. In 1913 Martinus Beijerinck repeated Van Leeuwenhoeks experiment and identified Clostridium butyricum as a prominent anaerobic bacterium in the sealed pepper infusion tube liquid. That Leeuwenhoek, one hundred years before the discovery of oxygen, for practical purposes, there are three categories of anaerobe, Obligate anaerobes, which are harmed by the presence of oxygen. Aerotolerant organisms, which use oxygen for growth, but tolerate its presence. Facultative anaerobes, which can grow without oxygen but use oxygen if it is present, some obligate anaerobes use fermentation, while others use anaerobic respiration. In the presence of oxygen, facultative anaerobes use aerobic respiration, without oxygen, some of them ferment, there are many anaerobic fermentative reactions. This is only 5% of the energy per molecule that the typical aerobic reaction generates. Since normal microbial culturing occurs in air, which is an aerobic environment. Hydrogen then reacts with oxygen gas on a palladium catalyst to more water. The issue with the Gaspak method is that a reaction can take place where the bacteria may die. The thioglycollate supplies a medium mimicking that of a dicot, thus providing not only an anaerobic environment, complex multicellular life that does not need oxygen is said to be rare, however there are examples of such organisms. Some organisms metabolise primarily using glycogen, for example the Nereid s and some polychaetes, or the juvenile Trichinella spiralis parasites. )

10.
Superoxide dismutase
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Superoxide dismutase is an enzyme that alternately catalyzes the dismutation of the superoxide radical into either ordinary molecular oxygen or hydrogen peroxide. Superoxide is produced as a by-product of oxygen metabolism and, if not regulated, hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase. Thus, SOD is an important antioxidant defense in all living cells exposed to oxygen. One exception is Lactobacillus plantarum and related lactobacilli, which use a different mechanism to prevent damage from reactive, where M = Cu, Mn, Fe, Ni. In a series of reactions, the oxidation state and the charge of the metal cation oscillates between n and n+1, +1 and +2 for Cu, or +2 and +3 for the other metals. Irwin Fridovich and Joe McCord at Duke University discovered the activity of superoxide dismutase in 1968. SODs were previously known as a group of metalloproteins with unknown function, for example, likewise, Brewer identified a protein that later became known as superoxide dismutase as an indophenol oxidase by protein analysis of starch gels using the phenazine-tetrazolium technique. There are three families of superoxide dismutase, depending on the protein fold and the metal cofactor, the Cu/Zn type, Fe and Mn types. Copper and zinc – most commonly used by eukaryotes, including humans, the cytosols of virtually all eukaryotic cells contain an SOD enzyme with copper and zinc. For example, Cu-Zn-SOD available commercially is normally purified from red blood cells. The bovine Cu-Zn enzyme is a homodimer of molecular weight 32,500 and it was the first SOD whose atomic-detail crystal structure was solved, in 1975. It is an 8-stranded Greek key beta-barrel, with the site held between the barrel and two surface loops. The two subunits are tightly joined back-to-back, mostly by hydrophobic and some electrostatic interactions, the ligands of the copper and zinc are six histidine and one aspartate side-chains, one histidine is bound between the two metals. Fe-SOD can also be found in the chloroplasts of plants, the 3D structures of the homologous Mn and Fe superoxide dismutases have the same arrangement of alpha-helices, and their active sites contain the same type and arrangement of amino acid side-chains. They are usually dimers, but occasionally tetramers, manganese – Nearly all mitochondria, and many bacteria, contain a form with manganese, For example, the Mn-SOD found in human mitochondria. The ligands of the ions are 3 histidine side-chains, an aspartate side-chain. This has a structure built from right-handed 4-helix bundles, each containing N-terminal hooks that chelate a Ni ion. The Ni-hook contains the motif His-Cys-X-X-Pro-Cys-Gly-X-Tyr, it provides most of the interactions critical for binding and catalysis and is, therefore

11.
Peroxidase
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Peroxidases can contain a heme cofactor in their active sites, or alternately redox-active cysteine or selenocysteine residues. The nature of the donor is very dependent on the structure of the enzyme. For example, horseradish peroxidase can use a variety of compounds as electron donors and acceptors. Horseradish peroxidase has an active site, and many compounds can reach the site of the reaction. Because there is a very closed active site, for a such as cytochrome c peroxidase. While the exact mechanisms have yet to be determined, peroxidases are known to play a part in increasing a plants defenses against pathogens, peroxidases are sometimes used as histological marker. Cytochrome c peroxidase is used as a soluble, easily purified model for cytochrome c oxidase, the glutathione peroxidase family consists of 8 known human isoforms. Glutathione peroxidases use glutathione as a donor and are active with both hydrogen peroxide and organic hydroperoxide substrates. Gpx1, Gpx2, Gpx3, and Gpx4 have been shown to be selenium-containing enzymes, amyloid beta, when bound to heme, has been shown to have peroxidase activity. A typical group of peroxidases are the haloperoxidases and this group is able to form reactive halogen species and, as a result, natural organohalogen substances. A majority of protein sequences can be found in the PeroxiBase database. Peroxidase can be used for treatment of waste waters. For example, phenols, which are important pollutants, can be removed by enzyme-catalyzed polymerization using horseradish peroxidase, thus phenols are oxidized to phenoxy radicals, which participate in reactions where polymers and oligomers are produced that are less toxic than phenols. It also can be used to convert toxic materials into less harmful substances, there are many investigations about the use of peroxidase in many manufacturing processes like adhesives, computer chips, car parts, and linings of drums and cans. Other studies have shown that peroxidases may be used successfully to polymerize anilines and phenols in organic solvent matrices

12.
Catalase
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Catalase is a common enzyme found in nearly all living organisms exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide to water and oxygen and it is a very important enzyme in protecting the cell from oxidative damage by reactive oxygen species. Likewise, catalase has one of the highest turnover numbers of all enzymes, one molecule can convert millions of hydrogen peroxide molecules to water. Catalase is a tetramer of four chains, each over 500 amino acids long. It contains four heme groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for human catalase is approximately 7, and has a broad maximum. The pH optimum for other catalases varies between 4 and 11 depending on the species, the optimum temperature also varies by species. Human catalase forms a tetramer composed of four subunits, each of which can be divided into four domains. The extensive hydrophobic core of each subunit is generated by an eight-stranded antiparallel b-barrel, with nearest neighbor connectivity capped by b-barrel loops on one side and a9 on the other. A helical domain at one face of the b-barrel is composed of four C-terminal helices, catalase was not noticed until 1818 when Louis Jacques Thénard, who discovered H2O2, suggested its breakdown is caused by an unknown substance. In 1900, Oscar Loew was the first to give it the name catalase, in 1937 catalase from beef liver was crystallised by James B. Sumner and Alexander Dounce and the weight was found in 1938. In 1969, the amino acid sequence of bovine catalase was discovered, then in 1981, the three-dimensional structure of the protein was revealed. The formation of bubbles, oxygen, indicates a positive result and this easy assay, which can be seen with the naked eye, without the aid of instruments, is possible because catalase has a very high specific activity, which produces a detectable response. Alternative splicing may result in different protein variants, Fe-E is a mesomeric form of Fe-E, meaning the iron is not completely oxidized to +V, but receives some stabilising electron density from the heme ligand. This heme has to be drawn then as a radical cation, as hydrogen peroxide enters the active site, it interacts with the amino acids Asn148 and His75, causing a proton to transfer between the oxygen atoms. The free oxygen atom coordinates, freeing the newly formed water molecule, Fe=O reacts with a second hydrogen peroxide molecule to reform Fe-E and produce water and oxygen. The reactivity of the center may be improved by the presence of the phenolate ligand of Tyr358 in the fifth iron ligand

13.
Microbiology
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Microbiology is the study of microscopic organisms, those being unicellular, multicellular, or acellular. Microbiology encompasses numerous sub-disciplines including virology, mycology, parasitology, microbiologists traditionally relied on culture, staining, and microscopy. However, less than 1% of the present in common environments can be cultured in isolation using current means. Microbiologists often rely on extraction or detection of nucleic acid, either DNA or RNA sequences, viruses have been variably classified as organisms, as they have been considered either as very simple microorganisms or very complex molecules. As an application of microbiology, medical microbiology is often introduced with medical principles of immunology as microbiology and immunology, otherwise, microbiology, virology, and immunology as basic sciences have greatly exceeded the medical variants, applied sciences. The existence of microorganisms was hypothesized for many centuries before their actual discovery, the existence of unseen microbiological life was postulated by Jainism which is based on Mahavira’s teachings as early as 6th century BCE. Paul Dundas notes that Mahavira asserted existence of unseen microbiological creatures living in earth, water, air, in 1546, Girolamo Fracastoro proposed that epidemic diseases were caused by transferable seedlike entities that could transmit infection by direct or indirect contact, or vehicle transmission. However, early claims about the existence of microorganisms were speculative, actual observation and discovery of microbes had to await the invention of the microscope in the 17th century. In 1676, Anton van Leeuwenhoek, who lived most of his life in Delft, Holland, observed bacteria and other microorganisms using a single-lens microscope of his own design. While Van Leeuwenhoek is often cited as the first to observe microbes, Robert Hooke made the first recorded microscopic observation, of the bodies of moulds. It has, however, been suggested that a Jesuit priest called Athanasius Kircher was the first to observe micro-organisms and he was among the first to design magic lanterns for projection purposes, so he must have been well acquainted with the properties of lenses. One of his books contains a chapter in Latin, which reads in translation – Concerning the wonderful structure of things in nature, here, he wrote who would believe that vinegar and milk abound with an innumerable multitude of worms. He also noted that material is full of innumerable creeping animalcule. These observations antedate Robert Hookes Micrographia by nearly 20 years and were published some 29 years before van Leeuwenhoek saw protozoa and 37 years before he described having seen bacteria. Joseph Lister was the first person who said infectious diseases are caused by micro-organism and was first person who used phenol as disinfectant on the wounds of patients. Cohn was also the first to formulate a scheme for the classification of bacteria. Louis Pasteur and Robert Koch were contemporaries of Cohn’s and are considered to be the father of microbiology and medical microbiology. Pasteur is most famous for his series of experiments designed to disprove the widely held theory of spontaneous generation

Thioglycolate broth is a multipurpose, enriched, differential medium used primarily to determine the oxygen …

Aerobic and anaerobic bacteria can be identified by growing them in test tubes of thioglycolate broth: 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube, but not the very top. 5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes, though, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.